1. Field of the Invention
The present invention relates to a method for controlling analog TV signal output and a computer system for playing DVDs with the above control method, so as to ensure application of protection technologies.
2. Description of the Related Art
With the rise of the digital image and multimedia, DVD players or DVD-ROMs are frequently integrated into personal computers, such as desktop or notebook. FIG. 1 is a schematic diagram showing the components of a DVD playing system in a computer system. Note that the other components of the computer system are omitted in FIG. 1 for concise illustration.
In FIG. 1, the DVD-ROM 10a is driven by DVD play application 10b to read the data from the DVD (not shown in FIG. 1). Thereafter, the data is processed by an image display control device 12a and displayed on the computer system (PC monitor 14) or a TV (not shown in FIG. 1) by outputting an analog TV signal to the TV via a TV signal output port 16.
The image display control device 12a may be a VGA (Video Graphics Array) control device with VGA control chip. In existing VGA control chips with TV output, image protection, such as that provided by Macrovision protection technologies, is also supported. Therefore, protection technology 12b is enabled when the DVD-ROM 10a is driven to read the DVD, thereby encode the analog TV signal to prevent infringement of the copyright.
However, protection technology is driven by the DVD play application. The DVD play application designed by vendors may be different. The DVD can be reproduced if the DVD play application is not started, and protection technology in the VGA control chip is not driven, since the analog TV signal is not encoded. Therefore, the computer system may be unable to protect copyrighted material.